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J. Agric. Food Chem. 2010, 58, 9112–9119 DOI:10.1021/jf101635b
Moderately Oxidized Oils and Dietary Zinc and r-Tocopheryl Acetate Supplementation: Effects on the Oxidative Stability of Rabbit Plasma, Liver, and Meat ALBA TRES,* RICARD BOU, RAFAEL CODONY, AND FRANCESC GUARDIOLA Nutrition and Food Science Department, XaRTA-INSA, Faculty of Pharmacy, University of Barcelona, Avinguda Joan XXIII s/n, 08028 Barcelona, Spain
The aim of this study was to assess the alterations in plasma, liver, and meat oxidative stability and R-tocopherol content when moderately oxidized sunflower oils were added to feeds and when feeds were supplemented with R-tocopheryl acetate (100 mg/kg) and Zn (200 mg/kg). The effects of cooking the meat and its subsequent refrigeration were also studied. When the content of primary oxidation compounds of the oil was high, rabbit plasma, liver, and meat R-tocopherol content was reduced and meat susceptibility to oxidation increased. The addition of oil with a high content of secondary oxidation compounds (oil heated at 140 °C, 31 h) to feed also led to an increase in meat susceptibility to oxidation, although it presented an R-tocopherol content similar to that of nonheated oil. Feed supplementation with R-tocopheryl acetate increased tissue R-tocopherol content and improved the oxidative stability of liver and meat. However, in the latter, it was less effective when oil heated at 55 °C was added. KEYWORDS: Heated oils; zinc supplementation; R-tocopherol; meat oxidation; cooking; TBA value; FOX; lipid hydroperoxides
INTRODUCTION
There is currently interest in supplementing animal feed with unsaturated fats. This procedure seeks to improve the nutritional value of meat and other animal products not only by increasing the content of polyunsaturated fatty acids (PUFA) but also by reducing the n-6/n-3 ratio (1). However, feed and animal producers should consider not only the fatty acid (FA) composition of fat ingredients added to feeds but also their degree of oxidation because unsaturated fats are prone to oxidization. At low temperatures, for instance, during the storage of these ingredients, the content of lipid hydroperoxides (LHP) increases until reaching a plateau (2). Thereafter, LHP decompose into secondary oxidation compounds. At high temperatures, the degradation of LHP is accelerated, so mostly secondary oxidation compounds are found in fat, as well as some polymeric compounds (2). High temperatures are achieved during common processes such as refining or frying. In fact, several fat co- and byproducts from the food chain obtained from processes involving high temperatures are currently used as animal feed ingredients (3). The addition of heated oils to animal feed does not lead to toxic effects when the fat content of the diets is not above the recommended dose for each animal species and when oil contains
